In a manner similar to an isotropic phase in a nematic liquid-crystal material (hereinafter, referred to as “non-liquid-crystal isotropic phase” in several cases), and also in a blue phase being one kind of an optically isotropic liquid-crystal phase, a Kerr effect (ΔnE=KλE2 (K: Kerr coefficient (Kerr constant), λ: wavelength)) is observed, being a phenomenon in which an electric birefringence value (birefringence value induced upon application of an electric field to an isotropic medium) ΔnE is proportional to a square of electric field E.
Research has been recently conducted actively on a mode in the electric field is applied in the optically isotropic liquid-crystal phase, such as the blue phase and a polymer-stabilized blue phase to exhibit electric birefringence (Patent literature Nos. 1 to 11, Non-patent literature Nos. 1 to 3). Further, a proposal has been made on not only application of the mode to a display device but also application to a wavelength variable filter utilizing electric birefringence, a wavefront control element, a liquid-crystal lens, an aberration correction element, an aperture control element, an optical head device or the like (Patent literature Nos. 6, 10 and 11).